I'm okay with a European Dr. Strange....makes him seem more exotic and sophisticated to American audiences. lol. Mysticism is more of the Old World anyway. Stark is the hero of today's America...self made genius technological billionaire. Strange is the hero of perhaps 1900 Europe?

Doctor Strange is associated with Eastern mysticism, specifically with a sort of pseudo-Indian/Tibetan kind. That's his "Old World" connection, which hopefully the film universe will manage to keep. Strange went to the Himalayas to seek a mystic who could cure him after nerve damage ended his surgical career and instead found a thousand year old sorcerer who was in need of an apprentice. It's a more profound story of redemption and personal change if the protagonist is a skeptical American who believes in science, abhors mysticism and eschews the metaphysical in favor of purely carnal delights. For a man like that to become Sorcerer Supreme is such a complete 180 that the audience is bound to be drawn along with him on the journey.